How Much Solar Do I need on My RV?
Having four big solar panels attached to the roof of our trailer attracts a bit of attention when we pull into most campgrounds. It is not uncommon for a new neighbor to walk over and ask about our solar setup shortly after we’ve parked. Solar is such an interesting idea and with the advent of “solar ready” trailers, it seems to be a topic on a lot of minds.
Based on our experiences with solar, we’d like to answer a few commonly asked solar questions relating to what we have installed, what electronics consume the electricity generated, and how we utilize our solar as full-time RVers.
Top Three Questions We Get About Solar Power
- My trailer is solar ready. Is that all I need?
- How much solar will I need?
- What does Home While We Roam run on solar power?
My Trailer Is “Solar Ready.” Is That All I Need?
Having a trailer that is marketed as “solar ready” is a great first step into solar. What solar ready means is a lot of the hard work related to wiring has already been done for you. To take advantage of your solar ready prewired port, you can purchase a solar ready kit that simply plugs into the port already installed on your solar ready trailer. This kit will generally include a solar panel or two, mounting feet and a charge controller. With this kit, you can immediately begin to charge the battery that came with your trailer using electricity harvested from the sun. Very cool!
Keep in mind that if you do go this route, your boondocking options will be limited to short off-grid trips while only using your 12-volt powered electrical systems. Using the battery that came with your trailer isn’t going to provide enough energy storage for long trips. Meaning, one or two panels won’t harvest enough energy to keep things running for long. Think, an overnight at a Walmart on the way to your next park.
Using solar ready, you would likely be able to run the following for a short time after the sun goes down:
- RV lighting
- Vent fans
- Furnace (short run time)
- 12-volt control for fridge running on propane
- If you are hoping to run major appliances like a coffee maker, keep reading!
How Much Solar Will I Need?
If you are considering solar, one of your follow-up questions will likely be, “How much do I need?” In this case, solar is being used as a catchall for all the components of an off-grid system. The first decision you need to make is about major appliances. Just like in your home, your trailer’s major appliances are 120-volt AC powered. A 12-volt battery can’t produce AC power which is where an inverter comes in and where solar stops meaning just solar panels. If you want to run 120-volt AC appliances, you will need an inverter to invert DC power of your batteries to AC power. You will also need a much larger battery bank than the single 12-volt deep-cycle battery that comes standard on most RVs.
This transition from using DC power to using DC and AC power is where most of the costs and technical sophistication comes into any solar project. It is possible to use a small, few hundred-watt inverter which would be good for charging a laptop, but if you want to run something like a microwave, which will draw 1,500 watts or more and have other AC systems running at the same time, you will need a much beefier inverter system.
What Our Solar RV System Includes
Our decision to be a fully off-grid-capable system meant we wanted to run all of our major appliances with the exception of the air conditioner on our own power. This meant we needed to have a healthy budget, a detailed plan, and lots of help from good friends. The major components of our system are:
- Solar panels
- Charge controller
- Battery monitor
- Inverter charger
We have four 100-watt polycrystalline panels installed on the front section of our camper’s roof. All solar panels serve a single purpose: They allow a user to harvest energy from the sun and turn it into electricity. Why are there types to choose from? It really comes down to efficiency.
Monocrystalline vs. Polycrystalline
When you evaluate solar panels for your project, you will need to make a choice between monocrystalline and polycrystalline. Since we recommend polycrystalline, let’s start there.
Polycrystalline solar panels are in the neighborhood of 10 percent less efficient than their monocrystalline counterparts. Depending on the manufacturer of the polycrystalline panel, you can expect a 10-15 percent conversion rate of sun energy to electricity whereas monocrystalline panels hover around 22 percent efficiency of sun energy to electricity.
What does that added efficiency mean practically? Not much. It may be the difference between a few minutes more Netflix time while we are boondocking at Walmart. Since the price between the two panel types can be as much as 30-50 percent more for monocrystalline, polycrystalline is our recommendation for now. We are hopeful for future gains that will enable us to recommend panels that are as efficient on your wallet as they are at converting sun energy, but we aren’t there just yet.
Home While We Roam Tip
You will also see solar options that include tilting or being flexible. Our recommendation is to save yourself extra work and extra budget by going with flat, nontilted, polycrystalline panels. Monocrystalline are priced at a premium and the efficiency gains of tilting your panels versus the effort of going up on the roof to tilt, is just not worth it. If you have the roof space, cover it with more polycrystalline panels to offset the efficiency issues.
Solar Charge Controller
We have heard it stated from many solar DIY enthusiasts and we will say it again here. Go with the most expensive MPPT charge controller your project budget can stand. We use Victron Energy’s BlueSolar Charge Controller 100/50 Charge Controller
A charge controller’s job is to regulate the power going into the batteries to prevent things like damage due to overcharging. The two most common types of charge controllers are a Pulse Width Modulation (PWM) and a Maximum Power Point Tracking (MPPT). MPPT controllers are the most modern and best technology for battery charging today.
The biggest benefit of an MPPT controller is its ability to convert excess voltage into amperage. Since panels can deliver many more volts than is required to charge your batteries, amperage is increased using that excess voltage which means less time to charge your batteries. Less time to charge your batteries is always a crucial feature especially when you are running off-gird during the winter with fewer daylight hours available. In this case, we do like paying a premium both for the features you get and for the efficient battery management of a high-quality charge controller.
We use Battle Born LiFePO4 Deep Cycle Batteries. Our current bank is 300 amp-hours. When it comes to battery banks, that amp-hours number is going to matter most. You need to ensure you have enough amp-hours to use your system in the way you want to while also balancing cost, storage location and potentially added weight to your rig.
This is how we decided to spend such a large percentage of our solar project budget on batteries. We looked at the most common options: lead-acid, AGM and lithium chemistry. We decided on the Battle Born lithium batteries for these reasons:
You can almost fully discharge these batteries without damaging them. That means that if you have a 100 amp-hour battery, you should expect to get nearly 100 amp-hours of power. If you compare that to a 100 amp-hour lead-acid battery that you can’t discharge below 50 percent, that means you really only get 50 amp-hours at best.
They are much lighter than traditional chemistry batteries. We replaced the 50-pound 100 amp-hour lead-acid battery our rig came with, with three LiFePO4 at 29 pounds each and had an incremental weight gain of 37 pounds and an incremental power gain of 250 amp-hours.
No maintenance. These batteries are sealed and never require a user to add water and worry about maintenance.
Life span – These batteries will last a long time. They come with a 10-year warranty and estimate that at least 75 percent of the battery capacity will remain after 3,000 charge cycles.
No venting required – Since they don’t need to be vented, it is safe to install a battery bank inside the rig. This increases your installation placement options and may help you use your space in a clever way.
Battery monitors don’t get enough love and we just can’t figure out why. While doing our research, we didn’t see them highlighted often enough so we want to highlight them here. Our battery monitor is something we use all the time, especially using the Victron App on our phones while connected via Bluetooth. You can always see what your battery charge is and the app does a great job of estimating remaining power based on your current load. Where the remote management really shines is when we have had our rig in storage. We jump out of the truck and before we even unlock the door to the camper, we already know if the system is running and the batteries are fully charged.
Our inverter charger is an Aims Power 3000 Watt 12V Pure Sine Inverter Charger w/9000W Surge
As you start to put together your solar project, you will probably find that after your battery bank, your inverter is going to take up the next largest percentage of your budget. It is also going to take up some space. When you get into the 3,000-watt inverter range, these things are big and heavy! Our inverter weighs in at 56 pounds!
Since we wanted to run all of our AC systems (except the air conditioning), we needed a big inverter with the ability to surge under heavy load. Since we wanted to be able to make popcorn while streaming a movie from our Plex media server, we needed at least 3,000 watts with the ability to surge beyond that for short times.
Pure Sine vs. Modified Sine
Since we do run sensitive electronics and you likely will as well, don’t consider an inverter that isn’t a pure sine inverter. This technology allows for a cleaner, less choppy sine wave. Sensitive electronics can be damaged by a modified sine inverter.
Most large inverters are actually inverter/chargers as they also facilitate charging the batteries when on shorepower. Note that the inverter itself takes some 12 volts of power to come on and begin charging, so if you do run your batteries very low, you may not have enough power to start the inverter’s charging process when you plug into shorepower. We learned this the hard way while in the snow in the Yosemite Valley. If that happens, you will have to wait until you harvest enough sun energy so your batteries have enough voltage to power the charger enough so it can start its charge cycle.
What We Run on Solar and Battery Power:
AC 120-volt systems:
- Two 40+-inch TVs
- Apple Mac Mini media server
- Wi-Fi router
- Celluar modem
- Nintendo Switch
- Hair dryer
- Coffee grinder
- Charge our Dyson vacuum, phones and other rechargeable stuff
DC 12-volt systems:
- Vent fans
- Radio/DVD player
What We Do NOT Run on Solar and Battery Power:
- Air conditioner – We wired it on a separate circuit so it physically can’t run on battery power.
- Refrigerator on AC instead of propane. Although we can run it, we don’t because it is a power hog.
- Space heaters – We can but don’t. It’s a total power hog.
How Long Can We Run on Solar?
How long we can run our battery on solar power is a tricky question. In perfect, sunny, conditions and with good conservation practices, we can run nearly indefinitely. Although conservation can sometimes be a bummer, when we are in a conservation scenario we are only using our major appliances as a convenience. If we are trying to stay boondocking as long as possible, it may look like this:
- 12-volt air vents running all day
- Make coffee in the morning with breakfast. No TV, no microwave, etc.
- Go out and hike and turn off all electrical systems to ensure a full battery charge for later
- At lunch, use the microwave, run the TV for a half- hour or so
- At dinner, use the appliances as needed
- After the sun sets, watch a movie on TV but keep a close eye on the battery charge
We generally don’t worry about conservation if we are just staying the night in a parking lot somewhere while heading to a Good Sam Resort where we know we have full hookups in our future. It is great fun to run the margarita machine, entertainment system and microwave without a care. However, in this mode, even with 300 amp-hour battery bank, we deplete the batteries significantly in just a few hours.
Is Solar Worth It?
Yes! As long as you are OK with your return on investment taking a really long time, if ever. The freedom that having an off-grid system provides is not something you can easily quantify. We can tell you for sure that after having this technology in our camping lives, it is not something we will be willing to go without. If you are interested in going solar, we encourage you to explore your own options for solar-powered trailer life. You won’t regret the freedom you create for yourself and your family.